Water Quality of the Vadose and Saturated Zone in Part of the Sedimentary Aquifer System of Kopais Basincentral Greece

This paper aims at presenting the study of groundwater quality and more specifically of the aquifer and the leachates of sub-soil at the central part of Viotikos Kifisos river basin-central Greece. Quality characterization of the aquifer system was based on the principles set in the Water Framework Directive-WFD (2000/60/EC), adopting as standards the maximum admissible concentrations for water intended for human consumption. Results were based on the analysis of hydrochemical determinations carried out in 194 water samples collected from the vadose zone (through a prototype sampling system) and the shallow wells of the saturated zone, over the period 2009-2011. Spatio-temporal study of water quality characteristics was performed and the hydrochemical character of water samples was assessed using the expanded Durov diagram. As suggested by the analysis of the hydrochemical data, the bedrock of the basin that is formed of carbonate rocks and a schist-chert formation with ultrabasic blocks (mélange), control the dominant hydrochemical character of the analyzed water samples. Hence a strong calcium bicarbonate character prevails, whilst the existence of iron, manganese and nickel is characteristic and attributed to weathering of the lateritic horizons and supplementary to the weathering of ultrabasic blocks. Intensive agriculture that is the dominant activity in the wider region is clearly depicted especially in the vadose zone leachates, in the form of elevated ammonium concentrations that often exceed the maximum admissible concentration for water intended for potable use. In addition, nitrate concentrations in the saturated zone of the sedimentary aquifer system exceed the respective threshold in several cases.